25 Jul 2022

Ex N Motor Repair Minimises Cost and Disruption

HOUGHTON INTERNATIONAL was commissioned by Sabic, a Teesside-based petrochemical manufacturing company, to overhaul a 250kW, 3.3kV 4-pole Ex N GEC motor used in its Olefins 6 plant, the second largest liquid naphtha cracker plant in Europe.

Initially, the customer requested an inspection and report on the condition of the motor. The motor was received from the customer in poor condition externally with substantial corrosion across the entire surface of the unit, but upon dismantling, the internal components were found to be clean, with little ingress evident in the windings. It was suspected that this was the first time the motor had been dismantled since the original installation other than for routine bearing oil changes. 

Based on these findings, Houghton International recommended a complete in-depth overhaul of the motor at its IECEx certified facility by a team of experienced electromechanical engineers. The overhaul consisted of stripping down and steam cleaning the motor, stoving the stator windings and dynamically balancing the rotor to ISO grade 2.5. Being an Ex motor, the mandatory hazardous area checks were also carried out, with a full report produced at the end.

Remedial repairs to the covers were also carried out, and they were shot blasted and primed. A new sound baffle cover, cooling fan locking nut and new gaskets were manufactured to specification, and the entire unit was rebuilt. 

Following the rebuild, the motor underwent full testing, including a Baker test which ran a complete cycle of tests to ensure the integrity of all motor windings, an overall broad test run, and monitoring of vibration and all bearings before being returned to the customer's site. 

To begin with, the customer thought the existing motor was beyond economical repair because of the external damage, and a new motor would be required. However, the overhaul minimised the cost implications and disruption to the customer.

Furthermore, midway through the overhaul, the customer requested a much quicker turnaround. Houghton International was able to meet the customer's demands and deliver the overhauled motor on time, ahead of the original schedule.